1. Field
The present embodiments relate to a magnetic detection device including a magnetoresistance effect device, and more particularly to a magnetic detection device capable of switching over a 1-output mode and a 2-output mode to be adapted for dipole detection.
2. Description of the Related Art
FIG. 20 is a circuit diagram of a known magnetic detection device. The known magnetic detection device comprises a sensor section S and an integrated circuit (IC) 1. The magnetic detection device shown in FIG. 20 is a sensor adaptable for dipole detection. The sensor section S comprises a first bridge circuit BC1 including two first magnetoresistance effect devices 2, e.g., GMR devices, each of which has a resistance value that changes depending on an external magnetic field in the (+) direction, and a second bridge circuit BC2 including two second magnetoresistance effect devices 3, e.g., GMR devices, each of which has a resistance value that changes depending on an external magnetic field in the (−) direction. The term “external magnetic field in the (+) direction” means an external magnetic field in one arbitrary direction. More specifically, in the circuit of FIG. 20, it means an external magnetic field acting in such a direction that the resistance value of the first magnetoresistance effect device 2 is varied, but the resistance value of the second magnetoresistance effect device 3 is not varied (namely, the device 3 acts as a fixed resistance). The term “external magnetic field in the (−) direction” means an external magnetic field acting in a direction opposite to the external magnetic field in the (+) direction. More specifically, in the circuit of FIG. 20, it means an external magnetic field acting in such a direction that the resistance value of the second magnetoresistance effect device 3 is varied, but the resistance value of the first magnetoresistance effect device 2 is not varied (namely, the device 2 acts as a fixed resistance).
As shown in FIG. 20, each of the two first magnetoresistance effect devices 2 constitutes a serial circuit in combination with a fixed resistance device 4. Two serial circuits are connected in parallel to constitute the first bridge circuit BC1. Output terminals of the two serial circuits constituting the first bridge circuit BC1 are connected to a first differential amplifier 6. Also, as shown in FIG. 20, each of the two second magnetoresistance effect devices 3 constitutes a serial circuit in combination with a fixed resistance device 5. Two serial circuits are connected in parallel to constitute the second bridge circuit BC2. Output terminals of the two serial circuits constituting the second bridge circuit BC2 are connected to a second differential amplifier 7.
The integrated circuit 1 includes in addition to the differential amplifiers 6 and 7, Schmidt-trigger comparators 12 and 13, latch circuits 8 and 9, etc. Detected signals of the external magnetic field are output from external output terminals 10 and 11.
In the magnetic detection device shown in FIG. 20, when the external magnetic field in the (+) direction is exerted on the magnetic detection device, the resistance values of the first magnetoresistance effect devices 2 constituting the first bridge circuit BC1 are varied, whereupon an output of the first bridge circuit BC1 is differentially amplified by the first differential amplifier 6. Accordingly, a (+) magnetic-field detected signal is generated and outputted from the first external output terminal 10. On the other hand, when the external magnetic field in the (−) direction is exerted on the magnetic detection device, the resistance values of the second magnetoresistance effect devices 3 constituting the second bridge circuit BC2 are varied, whereupon an output of the second bridge circuit BC2 is differentially amplified by the second differential amplifier 7. Accordingly, a (−) magnetic-field detected signal is generated and outputted from the second external output terminal 11.
Thus, the magnetic detection device shown in FIG. 20 is a dipole-detection adapted sensor which can detect any of the external magnetic fields in the (+) direction and the (−) direction.
The related art with respect to the present invention includes Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-77374, Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-180286, Patent Document 3: Japanese Unexamined Patent Application Publication No. 2005-214900, Patent Document 4: Japanese Unexamined Patent Application Publication No. 2003-14833, Patent Document 5: Japanese Unexamined Patent Application Publication No. 2003-14834, Patent Document 6: Japanese Unexamined Patent Application Publication No. 2003-121268, and Patent Document 7: Japanese Unexamined Patent Application Publication No. 2004-304052.
The known magnetic detection device shown in FIG. 20 is used in a 2-output mode in which the (+) magnetic-field detected signal and the (−) magnetic-field detected signal are separately outputted from the first external output terminal 10 and the second external output terminal 11, respectively.
Meanwhile, it is often needed to use the magnetic detection device in a 1-output mode in which only the first external output terminal 10, for example, is employed, and the (+) magnetic-field detected signal and the (−) magnetic-field detected signal are both outputted from the first external output terminal 10.
In order to be adapted for such need, the known magnetic detection device requires the circuit configuration of the integrated circuit 1 to be rearranged depending on the 1-output mode or the 2-output mode, thus resulting in an increase of cost.